Manufacture of hydrazine



Jan. 8, 1924.

R. A. JOYNER MANUFACTURE OF HYDRAZINE Zyyzmf Patented Jan. 8, 1924.

UNITED STATES PATENT OFFICE.

DELAWARE.

ASSIGNOB TO E. I. DU POM A CORPORATION 01! MANUFACTURE OF HYDRAZINE.

Application med January 1c, 1923. Serial 1%. 813,481.

To all whom it may concern:

Be it knoviqn that I, REGINALD ARTHUR Jomn, a subject of the King of Great Britain and Ireland, and residing at Ardeer 5 Factory, Stevenston, Ayrshire,

have invented. certain new anduseful Improvements in and Relatin to the Manufacture of Hydrazine, of w ich the followin isa SPGCIfiCatlOIL l .lhis invention relates to the manufacture of hydrazine. I

Several methods are available for the pre aration of this substance, but that dealt wit in the present application is one commonl employed on the commercial scale utilizing sodium hypochlorite and ammonia with a catalyst w h form of ordinary glue. The usual-way in which this process is operated is to heat a mixture of strong ammonia, glue and dilute sodium hypochlorite solution. The reaction takes place in two stages which may be represented by the equations (1) and (2).-

In the first stage the sodium hypochlorite and ammonia react formi g chloramine, and, in the second stage, this chloramine reacts with a further proportion of ammonia to form hydrazine.

Reaction (1) takes place quantitatively, but besides reaction (2) another reaction takes place between the chloramine and am- 5 monia to form ammonium chloride and nitrogen. This reaction may be represented by the equation:

(3) 3NH,C1+-2NH =3NH,C1+N,.

Reaction (2 only takes place to a large extent when t e ammonia 1s in very large excess and is accelerated by the presence of a catalyst such as glue, otherwise nearly all the chloramine formed in (1) reacts according to equation (3).

The process above described is the subject-matter of Raschigs British Patent No. 139 of 1908. I

When .the amount of ammonia is limited to that required by the two equations (1) and (2) the yield of hydrazine calculated on the sodium hypochlorite added is only Scotland,

process referred to above neces ordinarily takes the.

' output of about 5 per cent, even in the presence of glue, while when 20 times that amount of amltnonia is employed the yield is 65 per cen The manufacture of hydrazine with such a large excess of ammonia by means of the itates the use of much plant for the evap ration of the excess of ammonia and the condensation of it again in solution of such a concentration that it can be used over again. The method would be discontinuous and would require considerable amount of labor.

The object of the present invention is to provlde an improved process whereby greater yields of hydrazine are obtained by ensuring a high local concentration of ammonia at the oint where the interaction between the ch oramine and ammonia takes place.

Another object of this invention is to pro vide an im roved process whereby a greater drazine is obtained by the use of a specia y prepared catalyst.

A further object of the invention is to provide an apparatus which will enable high yields of hydrazine to be obtained by means of a high local concentration of ammonia and will allow of the same ammonia being passed again and again through the zone of high concentration.

My invention consists, in the first place, in the improvement of the process of preparin hydrazine from ammonia and .sodium ypochlorite with the aid of a catalyst, by ensurin the localization of the ammonia used to t e region where the reaction is taking place.

The invention also consists in an apparatus for carrying out the process referred to in the preceding paragraph comprising a tower into which the ammonia and hypochlorite can be fed in such are intimately brought into contact with unused ammonia through a considerable length of the tower and are finally introduced, for the carrying out of the main reaction, into a part of the tower in which they must necessarily remain for a comparatively long time.

The invention also proved method and in consists in the imthe improved appaa way that they lid rates for th reduction of hydrazine hereinatter descri ed.

e accompanying diagratic drawing'represents an apparatus which-may be employed accorg to the present invention.

1 ing the invention into efiect in In carry the form illustrated by way of example, a

tower suitable for an output of d'gallons an hour of a dilute solution of hydrazine hydrate is constructed as follows he tower is formedlof' a cylinder (2 or" iron or like metal which is not attacked by hydrazine. This is conveniently 20 feet high and 4 inches dieter and is packed with pce b or other suitable packing material. The next section of the tower is a trap c of about 1 the'same diameter as the lower portion of the tower. A. pipe d leads from approximately the top of this trap to the top of t e lower section a and it may pass internally through the trap as shown. Above the trap is a further section e about 6 feet high and four inches diameter which is also packed with pumice or other suitable packing material f.

In the bottom section a a 1-inch iron tube 9 adapted to be joined to a steam supply pipe entersthe tower about a yard from the top of the section a the bottom. branch ways with pose of acting as a blow-oh and the other tor connection with a covered hydrazine receiver k suitably placed below the tower into which receiver hydrazine liquor flows from the section a by way of the pipe 5. By means monia bein expelled before the reaction is of this aforesaid pipe g steam heat ng may complete. sthe strong ammoniacal solution be employed for warming-the sectlon a of .fl f the tower the tower on starting.

e trap or middle section 0 of the tower is provided with a coil Z for the circulation of cooling or warming fluid as desired. The top-section e of the tower has fitted therein another cooling coil m.

he top and middle sections are joined by a pipe a passing from a place near the bottom of the top section e to the vicinit of the bottom of the middle section 0. h top and lowest sections are joined by an external pipe or side tube 42 passing from the bottom of the top section to the top of the bottom section. Above the top of the column two feed tanks p and q are arranged, one (p) of which contains a mixture of catalyst and dilute aonia of a strength about 1.5 normal as regards ammonia and containing 1.5 gm. cl glue per litre. 'lh glue is prepared in the following way Two litres of 20% glue solution containing s. of hydrochloric acid gas are boiled uner a reflux for one hour, then sodium hydroxide solutionis added till the mixture gallon capacity, and of ere it is provided with 1 cocks, one 2' for the pur-.

anno nce is allraline to'phenolphthalein. The concenm t the catalyst is calculated in tennis ofmglue originally prnt.

he other tank 5; contains dilute sodium hypochlorite of about 0.8 normal. From these vessels the liquids are fed down the tower by the pipes r and and equal rates.

In starting the been heated up strong solution or ammoma, say 18 per cent,

s'respectively at constant process after connection may be made.

tel

dispensed with there is a danger of the am ows down the bottom ortion a t e ammonia is expelled and passes up through the side tube 1) connecting the top and bottom sections c and a respectively and 1s ire-dissolved in the liquid flowing down the to% section e.

y this means the concentration of the ammonla in the trap is maintained at about 18 per cent.

l hen once the maintains its own temperature and must generally be cooled so. that is kept between 40 and 45 C. time the amount of ammonia in the system is more than can be dissolved and a little of the trap liquor is run or as by the drain cock w of the trap c. This ammonia can be used for making up fresh solutions for the feed tank.

Instead of having a pipe 9 carrying steam to heat up the bottom section of the tower steam may be passed into the hydrazine recelver and may be allowed directly to ass up into this bottom section and I :the products of the reaction are diluted conon lessening siderably by the steam condensed.

The yield of hydrazine obtained by the use of this apparatus is about 65 'per cent of the theoretical possible from the sodium hypochlorite used. This result is obtained with an overall ratio of molecules of ammonia to chlorine of about four to one, theory requiring two" to one, while to obtain the same yield hitherto a ratio of 45 to 1 was required.

The yield of hydrazine on the ammonia consumed is also high, being about per cent.

. n keeping the concentration of the ammonia in the trap at about 18 per cent and the concentrations of the ammonia and the feed tanks so that one tank contains about a 1.2 normal solution of ammonia with 1.5

gm. of glue per litre and the other tank contains about a 0.6 normal solution of sodium hy ochlorite, the yield of hydrazine rises to a ut 7 3 per cent calculated on the sodium hypochlorite used. An increased yield on the ammonia consumed also results, bein now about 80 per cent. On account of t e dilution of the reaction substances the contents of hydrazine in the li uid emerging at the bottom of the tower is owcred.

' In the method described above no distillation of the reaction product is necessary. The process is continuous, the pro rtion of ammonia used is relatively sma and the labor costs are reduced.

It will be noted that in the present process although the excess ammonia, advisable to use in the carryin on of the second reaction, i. e. that between the chloramine formed in the first reaction, and the ammonia, is present, this exce ammonia is not provided until the second reaction is substantially about to take place. That is, the first reaction takes place in the top section 6 withoutsubstantial excess of ammonia, and it is not until the reacting substances reach the tra that the excess ammonia for preventing t e formation of ammonium chloride is provided. In this way, all those complications, such as excessive amounts of ammonia, a necessarily discontinuous process, and so on, which are inherent in a process in which the excess ammonia, and the hypochlorite are initially mixed, are avoided. Furthermore, as is evident, the ammonia in the trap is, in practical efiect, a stationary body through which the reacting materials flow, so that this ammonia practically does not have to be handled at all, it serving as a sort of catalyst or ammonia atmosphere, promotin the desired reaction. Thus the labor inci all the ammonia in a vessel with hypochlorsodium hypochlorite in the hydrazine b ent to adding its and then having to distill it off at the end is eliminated. Of course, there is a flow through the trap a, but, as is evident with the ammonia concentration in the trap c not falling, and this body of ammonia always being separate from the portion e, the excess ammonia is in practical efl'ect stationary as regards travel of the materials from p and 9' through the system. The portion 0. serves as a fraotionating column delivering ammonia to the trap through the tube '0. ing as herebefore indicated, with ammonia 1.5 normal and hypochlorite .8 normal fed at equal rates, the amount of ammonia becomes more than can be dissolved, it is advisable to draw off a little of the trap liquor, as herebefore referred to.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is 1. In the process for producing hydrazine by the reaction between ammonia and a hypochlorite in the presence of a catalyst, the steps of initiating the reaction without material excess of ammonia, and then passing the reacting substances into a body of concentrated excess ammonia, thus to provide, without material excess of ammonia in the initial reaction, for the reaction be- Sinco, when proceed;

tween the chloramine and ammonia in a hypochlorite in the presence of a catalyst,

the steps of initiating the reaction without material excess of ammonia, and then assing the reacting substances into a bad? of excess ammonia of a concentration of about 18%, thus to provide, without material excess of ammonia in the initial reaction, for the reaction between the chloramine and ammonia in a ammonia. Y

3. The continuous process of producing the reactlon between ammonia and a hypoc orite in the presence of a catalyst which comprises continuously flowin together the hypochlorite, and catalyst and di ute ammonia, without material excess of ammonia, thereby initiating the reaction, and then flowing the reacting substances into and throng a practically stationary body of concentrated excess ammonia thus to provide, without material excess of ammonia in the initial reaction, for the reaction between the chloramine' and ammonia in a high local concentration of ammonia, and continuously removingthe hydrazine from the body of concentrated ammonia.

- 4. The continuous process of producing hydrazine by the reaction between ammonia and a hypochlorite in the presence of a catalyst w ich comprises continuously flowing together the hypochlorite, and catalyst high local concentration of tionary body of excess ammonia, of a con-' centration of about 18% and at a temperature substantially between 40 and 50 0., thus to provide Without material excess of menace ammonia in the initial reaction, for the reaction between the chloramine and ammonia in a high local concentration of ammonia, and continuously removing the hydrazine from the body of concentrated ammonia.

In testimony whereof I have signed my name to this specification.

REGINALD ARTHUR JUYNJER. 

